China is working to get stalled talks about North Korea's nuclear weapons development back on track. This comes as South Korea's military is on the lookout for North Korean submarines that may have entered the South's waters.

Chinese Ambassador Ning Fukui arrived in Seoul Wednesday to discuss ways to bring North Korea back to the negotiating table. He was to meet with South Korea's chief nuclear negotiator, Deputy Foreign Minister Lee Soo-hyuk and other officials, then travel to Washington and Tokyo.

North Korea declined to participate in a fourth round of talks in September with China, South Korea, Russia, Japan and the United States. They are trying to persuade Pyongyang to abandon its nuclear weapons programs.

Speaking during a visit to Tokyo Wednesday, U.S. Deputy Secretary of State Richard Armitage said it is most important that China continue to lead diplomatic efforts on the nuclear dispute. He listed other key elements to the effort.

"And, number two, make sure that North Koreans will not see us get impatient or nervous, that we're steady in the long run, we'll prevail on this and they'll come to know it. Third of all, to make sure we are very true to our allies in the Republic of Korea and make sure we share fully and completely with them all of our thoughts on this," said Mr. Armitage.

Also Wednesday, defense officials in Seoul said navy ships have been hunting for two North Korean submarines thought to have entered the South's waters. But they say there has been no trace of the subs since the massive search began Sunday off the east coast.

South Korean military officials have raised doubts about the credibility of the intelligence on the submarines, which apparently came from the United States.

In the past, the North has used subs to slip spies into South Korea.

In another sign of the prickly state of North Korea's international ties, South Korea's Red Cross on Wednesday said Seoul might reject Pyongyang's request for 100,000 tons of fertilizer.

Seoul is delaying the shipment because North Korea has boycotted talks with it.

The two Koreas technically remain at war. However, in recent years, the South has provided aid to Pyongyang, including fertilizer to help improve meager harvests in North Korea.

Analyst Kim Tae-woo, at the Korean Institute for Defense Analysis in Seoul, says South Korea may delay the shipment as part of its strategy in dealing with the North.

"That doesn't mean any policy shift on the part of the South Korean government," said Kim Tae-woo. "The [South] Korean government is waiting for some clue on which South Korea can justify its assistance to North Korea, so that doesn't mean any major shift in ... policy."

He notes that four years ago after the North and South Korean navies exchanged gunfire along their maritime border, South Korea continued to send aid across the border.